Katy Perry was Moe's girlfriend. When Moe found out he would be house-sitting for the Simpsons while they were vacationing in Hawaii, he invited her to see him at 742 Evergreen Terrace, telling her it was his bachelor pad. When Katy got there, the Simpsons still hadn't left on their vacation, having been delayed by the arrival of Mr. Burns. Katy then asked what everyone was doing in her boyfriend's house.

When Katy saw that Mr. Burns was mad at Homer for lying about being injured so he could go to Hawaii, she gave Burns a hug and kiss, which prompted him to calm down and forgive Homer. She, along with Burns, Moe and the Simpsons, began to sing "The Thirty-Nine Days of Christmas". Moe then wanted to give Katy a kiss, but decided to kiss her belly button because that was as high as he could reach. After Moe started kissing, Katy told him that wasn't her belly button he was kissing. Moe then broke off the kiss, but Katy said she didn't tell him to stop.